Amyloidosis broadly encompasses a variety of diseases that are characterized by the extracellular or intracellular deposition of amyloid proteins in tissues and/or organs. Amyloids are insoluble fibrous protein/peptide aggregates and their deposition may occur in localized sites or systemically. The fibrillar composition of these deposits is an identifying characteristic for the various forms of amyloid disease. In some cases the amyloid protein/peptide accumulates intracellullary, resulting in cell dysfunction and ultimately cell death. Examples of intracellular amyloid proteins include α-synuclein, forming Lewy bodies in Parkinson's disease, and huntington, forming neuronal inclusions in Huntington disease. The pathogenesis of Alzheimer's disease (AD), the most common of the amyloid related neurodegenerative disorders, is linked to the cleavage of the amyloid precursor protein generating the amyloid-β (Aβ) peptide which undergoes a shape change into a pathological conformer having a high β-sheet content. Intracerebral and cerebrovascular deposits composed primarily of fibrils of the pathological Aβ peptide are characteristic of both familial and sporadic forms of AD. In addition to Aβ, abnormally phosphorylated tau protein forms toxic oligomeric structures and neurofibrillary tangles in AD. Similar to AD, prion-associated diseases, such as Creutzfeld-Jacob disease, have also been characterized as amyloid diseases. The pathogenesis of prion disease is linked to a change of the cellular prion protein (PrPC) into the disease associated PrPSc (Sc for scrapie). Currently, there is no effective therapy for any of these disorders.
An active area of translational research and current clinical trials for amyloid disease has focused on immunotherapy, using both passive and active immunization against amyloid proteins, particularly Aβ in AD (Wisniewski et al., “Amyloid-β Immunization for Alzheimer's Disease,” Lancet Neurol 7:805-811 (2008)). Although immunotherapy holds great promise as a means of reducing amyloid deposition, it, unfortunately, has been accompanied by major obstacles. Specific problems associated with immunotherapy that were identified in a clinical trial for AD include the potential of toxicity from encephalitis (related to excessive cell mediated immunity), the immunological targeting of both the normal and abnormal Aβ peptide, the failure to address tau related pathology, and the apparent poor efficacy. Moreover, although autopsy data from this early immunotherapy vaccine trial suggested that many patients had a significant reduction in amyloid burden, these patients exhibited only minor cognitive benefits (Wisniewski et al., “Amyloid-β Immunization for Alzheimer's Disease,” Lancet Neurol 7:805-811 (2008) and Holmes et al., “Long Term Effects of Aβ42 Immunization in Alzheimer's Disease: Immune Response, Plaque Removal and Clinical Function,” Lancet 372:216-223 (2008)). Therefore, an immunotherapeutic approach that can effectively reduce amyloid burden and overcome the aforementioned problems is warranted.
The present invention is directed to overcoming these and other deficiencies in the art.